Insight Product Company offers Quasi-continuous powerful millimeter
(mm-wave) and sub-millimeter (sub-mm wave) Orotron Generators which can
be used for both continuous wave (CW) and pulsed electron spin resonance
(ESR) and electon paramagnetic resonance (EPR) experiments. Below are
the specs:

-Available frequencies: 120-370 GHz
-Excellent long term and short term stability (up to 10-8)
-Allows phase manipulation, so that each consecutive pulse signals can
be of the same phase as the previous one, shifted by 90 degrees, or shifted
by 180 degrees.
- Pulse duration: 50ns – 1 ms
-Typical output power: 30-50 mW